Charity fundraising balls and balloon raffles etc :)

The charity I work for has a fundraising ball coming up for which we are the beneficiary (sorry crap sentence there). We don't really do this kind of fundraising much, but it has been suggested that we run some kind of raffle type thing (as well as a normal raffle), where a piece of paper is put inside each one of lots of balloons, some of which are winners for different amounts, and people buy them/bid for them etc.

Does anyone have any experience of how this works exactly? Anyone been to an event where this happened and can remember it?